1. Industrial Field of the Invention
The present invention relates to a plurality of kinds of wax products fractionated from raw wax in a solid state through solid-liquid extraction so that they have different melting points, a particular temperature range between a melting starting point and a melting ending point, and a specific melting energy, such fractionated wax products being suitable for thermosensitive paper, thermo-sensors, hot-melt adhesives and the like.
2. Description of the Prior Art
In the related field of industry, there is great demand for wax products having different melting points which are fractionated, in accordance with molecular weights, from polyolefine of a low polymerization degree manufactured through Ziegler process, coal synthetic wax, synthetic wax such as Fischer-Tropsch wax, petroleum paraffin wax or natural wax. Recently, wax which has a small range of melting points, i.e., a small range between a melting starting point and a melting ending point and whose melting energy is large is especially in demand so as to be used for thermo-sensors, thermosensitive paper, heat accumulators, hot-melt adhesives and the like.
Wax products made from Ziegler process polyolefine of a low polymerization degree, i.e., polyethylene of a low polymerization degree which is a byproduct when manufacturing polyethylene and polyethylene of a low polymerization degree produced by polymerizing ethylene or polymerizing ethylene as a main component are available at present. However, they do not meet the above-mentioned industrial demand particularly because they are far from satisfactory in respect of the range of melting points.
Conventionally, some kinds of wax products having different melting points have been produced by solvent fractionation of petroleum wax, but they have problems in relation to various desired melting points and a range of the melting points, and also, a producing method thereof is not favorable. For example, a recrystallization method with an organic solvent, a sweat-out method or the like have been suggested. In the organic solvent recrystallization method, it is necessary to use a large amount of the solvent and separate precipitated crystals from a solution through filtration. Since the precipitated wax is in a gel state, filtration cannot be easily performed, and this step of filtration has been an industrial drawback. In the sweat-out method, the procedure involves complication because it requires, for instance, high-temperature long process, and resulting wax has low-grade purity and is limited to certain uses. In the present situations, therefore, there can be observed almost no technique to provide wax Products of various kinds whose melting characteristics satisfy the demand, and there can be found almost no wax products having desired melting points and particular melting characteristics so as to meet the requirements in actual use.
Especially, there has been neglected research for a method of fractionating polyolefine wax of a low polymerization degree which is a byproduct when manufacturing polyolefine such as polyethylene in order to obtain wax products having different molecular weights. Consequently, fractionated wax products having favorable characteristics as described above have not been found out.
The present invention has an object to provide a method of producing one kind or a plurality of kinds of wax products having different melting points, i.e., different average molecular weights, from raw wax such as Ziegler synthetic wax or paraffin wax in a simple manner.